Latch assembly



Dec. 15, 1964 R. E. LAGERQUIST 3,161,037 Q LATCH ASSEMBLY Filed April 24, 1965 2 Sheets-Sheet l FIG.|

FIG. 2

ROGER E. LAGERQUlST INVENTOR.

ATTORNEYS 1964 R. E. LAGERQUIST 3,161,037

LATCH ASSEMBLY Filed April 24, 1965 2 Sheets-Sheet 2 FIG. 5

FIG. 6

ROGER E. LAGERQUIST INVENTOR.

W/Mw ATTORNEYS ited States Patent Ofiice 3,161,037 Patented Dec. .15., 1964 3,161,037 LATCH ASSEMBLY Roger E. Lagerquist, Goleta, Califl, assignor to Edgerton,

Gerrneshausen & Grier, Inc, Boston, Mass, a corporation of Massachusetts Filed Apr. 24, 1963, Ser. No. 275,281 4 Claims. (El. 76-169) This invention relates to latch assemblies and more particularly to latch assemblies for use in sealing the ends of small cylinders which may be used to house various devices.

Many small substantially cylindrically-shaped devices may be housed in small metal or plastic cylinders, the ends of which may be permanently sealed, capped with removable caps, or plugged with removable plugs. Sometimes, it is desired that such sealing means be removable, but only by authorized personnel. In short, such sealing means must not only be removable, but must be as tamper-proof as possible. In the case of cylindrically-shaped thermoluminescent dosimeters, such a housing and sealing means are desired so as to prevent tampering with and possible damage to the dosimeter. This is particularly necessary in a thermoluminescent dosimetry system designed to eliminate human error to the maximum extent possible. I have devised a latch assembly for sealing the end of a small cylinder which solves this problem. My latch assembly contains a number of novel features which make it extremely difiicult for one to remove without the proper key once it is installed in a cylindrical case. In summary my latching system comprises a latch assembly and a specially shaped key for sealing the end of a small cylinder. An interior groove is cut parallel to and near the end of the cylinder and a limit stop is disposed between the groove and the end to limit the inward movement of the latch assembly. The latch assembly includes a latch having a latch arm adapted to engage the groove in the cylinder, means for maintaining the latch arm in engagement with the groove and for disengaging the latch arm in response to operation of the key and cooperating means for receiving the key and for holding the key axially fixed in position after disengagement of the latch arm, so the latch assembly may be removed by pulling the fixedin-position key outwards.

Accordingly, it is an object of my invention to provide a latch assembly for sealing the end of a small cylinder, which assembly is easily removed by one having the proper key.

Another object of my invention is to provide a latch assembly for sealing the end of a small cylinder, which assembly is highly tamper-proof.

A further object of my invention is to provide a latch assembly for sealing the end of a small cylinder, which seal is substantially air and water tight.

Various other objects and advantages of the invention will become apparent from a perusal of the following specification and the drawings accompanying the same. In the drawings:

FIGURE 1 is a cross-sectional view in part of the latch assembly of my invention installed in the end of a cylinder, in the latched position;

FIGURE 2 is an end view of the latch assembly illustrating the shape of the key hole;

FIGURE 3 is a side view of the key utilized with my latch assembly;

FIGURE 4 is a plan View of the key of FIGURE 3;

FIGURE 5 is a cross-sectional view in part of the latch assembly of my invention installed in the end of a cylinder in the unlatched' position, together with the key of FIGURE 3; and,

FIGURES 6 and 7 are side and end views respectively of the latch guide utilized in the latch assembly of my invention.

FIGURE 1 illustrates cylinder here illustrated as being made of plastic with latch assembly 21 sealing end 22. Slot 23 is cut into the interior surface of cylinder 20 parallel to the plane of end 22. Near end 22, the interior surface of cylinder 20 is undercut'to provide limit stop 24 against which surface 25 rests when latch assembly 21 is pushed into cylinder 20.

Latch assembly 21 comprises a number of component parts which will now be described. Cylindrical end plug 26 is threadably fastened to cylindrical latch assembly housing 27 as illustrated. Housing 27 contains cylindrical spring retainer guide 28 for guiding the movement of cylindrical spring retainer 29 and spring 30 which seats against surface 31.

Positioned next to spring retainer 29 is cylindrical latch guide 32. Referring to FIGURES 6 and 7, latch guide 32 has slot 33 out along its axis with latch pin 34 mounted perpendicular to said slot, both as illustrated. Note that the cross-sectional view of latch guide 32 as seen in FIGURE 1 is taken along the line A-A of FIGURE 6 looking in the direction of the arrows. Cylindrical end 35 has a cavity 36 (see FIGURE 7) drilled in end 37 in the shape of a frustum of a right circular cone. The sectional view of cavity 36 appears in FIGURE 1. .The function of cavity 36 will be explained hereinafter.

Latches 38 slidingly fit in both sides of slot 33 of latch guide 32 and in contact with latch pin 34 as illustrated in FIGURE 1. Latch rocker arms 39 fit in latch rocker arm slot 40 as illustrated. Latch arms 41 extend through latch ports 42 of latch assembly housing 27 and engage slot 23 of cylinder 20.

In the latched position, O-ring 43 is compressed by the action of spring 30 and maintains an air and water tight seal between surfaces 44 and 45. Also spring 30 presses spring retainer 29 against tips 46 of latches 38 thereby maintaining latch arms 41 firmly engaged in slot 23. Also, latches 38 press against latch pin 34 forcing latch guide 32 to seat firmly against O-ring 43 which provides an airtight seal between surfaces 44 and 45.

FIGURE 2 illustrates surface 47 of cylindrical end plug 26 through which slot 48 is cut to receive key 49 of FIGURE 3. Key 49 is shaped to pass through slot 48 with its tip 56 fitting into cavity 36 of latch guide 32 as illustrated in FIGURE 5. Key 49 may have a handle 51, or not, as desired. Dimensions of key 49 are kept sulficiently small so that it must be made of special high strength material to have sufiicient strength to perform the necessary operations described hereinafter without breaking or deforming.

In operation, key 49 is inserted through slot 48 and tip 50 engages cavity 36. Pressure is exerted to compress spring 30 moving latch guide 32 to the left as illustrated in FIGURE 5. This breaks the seal between surfaces 43 and 44 and equalizes any pressure difference. Latch pin 34 forces latch rocker arms 39 to rotate within slot 40 as illustrated in FIGURE 5. Latch arms 41 swing out of engagement with slot 23 to the position illustrated, clearing inner surface 52 of cylinder 20.

Key 49 is then rotated one-quarter turn so that edges 53 and 54 contact inner conical surface 55 of cylindrical end plug 26. Latch assembly21 may then be withdrawn by exerting sufficient force to break the seal formed by O-ring 56 with inner surface 57 of cylinder 20. Note that cylindrical-end plug 26 is slotted as illustrated to receive O-ring 56.

Note that to unlatch latch assembly 21, a key with a tip 50 must fit into cavity 36 of latch guide 32. Next, pressure must be exerted axially along key 49 to disengage latch arms 41 from slot 23 and to position key 49 so it can be rotated one-quarter turn. Then key 49 is rotated one-quarter turn. Last, latch assembly 21 is withdrawn.

This series of steps makes latch assembly 21 highly tamper-proof. However, an authorized person who knows the foregoing steps can easily remove latch assembly 21 if he has a key 49.

Attempts to remove latch assembly 21 by prying through slot 43 or by striking cylinder 20 against a solid object only tend to seat latch arms 41 more firmly in slot 23. Further, key dimensions are critical. A counterfeit key 49 which is too long cannot be inserted far enough to be turned. One which is too short will not fully retract latch arms 41 and at the same time fit against conical surface 55 when attempting to withdraw latch assembly 21.

It will be understood that various changes in the details, materials and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

I claim:

1. A latching system comprising a latch assembly and a specially shaped key for sealing the end of a small cylinder having an interior groove parallel to and near the end of said cylinder and a limit stop disposed between said groove and said end for limiting the inward movement of said latch assembly, said latch assembly comprising:

a latch having a latch arm adapted to engage said groove;

first means including a housing for holding said latch,

a spring, and guide mean having a cavity specially shaped to receive the tip of said key, said first means being adapted to maintain said latch arm in engagement with said groove and to rotate said latch arm out of engagement with said groove and into said housing when said key is caused to move said guide means which thereupon compresses said spring and moves said latch causing said latch arm so to rotate; and

second means threadably fastened to said housing and having a shoulder to engage said limit stop, a special keyway to receive said key and a cavity specially shaped to hold said key axially fixed in position when said key is inserted through said keyway, is caused to move said guide means and is rotated out of alignment with said keyway, whereupon said latch assembly may be withdrawn from said cylinder by pulling said fixed-in-position key outwards.

2. A latching system as in claim 1 in which said cavity in said guide means is shaped like the frustum of a right circular cone and the tip of said key is adapted to fit snugly within said cavity.

3. A latching system as in claim 2 in which said second means comprises a plug threadably connected to said housing, said plug having a cavity on the side thereof opposite said keyway, said cavity having a first cylindrical inner surface and shoulder-adapted to fit said guide means, and a smaller cylindrical surface and a conical surface decreasing in diameter therefrom to said keyway, said key being further adapted to fit snugly and rotatingly within said smaller cylindrical and conical surfaces.

4. A latching system as in claim 3 further comprising:

an O-ring disposed between said plug and said cylinder;

and

an O-ring disposed between said plug and said guide.

References Cited by the Examiner UNITED STATES PATENTS 154,408 8/74 McKnight -168 X 858,781 7/07 Benedict 70-169 1,060,693 5/ 13 Mueller. 3,126,728 3/64 Nehls 70169 FOREIGN PATENTS 8,917 5/89 Great Britain.

ALBERT H. KAMPE, Primary Examiner. 

1. A LATCHING SYSTEM COMPRISING A LATCH ASSEMBLY AND A SPECIALLY SHAPED KEY FOR SEALING THE END OF A SMALL CYLINDER HAVING AN INTERIOR GROOVE PARALLEL TO AND NEAR THE END OF SAID CYLINDER AND A LIMIT STOP DISPOSED BETWEEN SAID GROOVE AND SAID END FOR LIMITING THE INWARD MOVEMENT OF SAID LATCH ASSEMBLY, SAID LATCH ASSEMBLY COMPRISING: A LATCH HAVING A LATCH ARM ADAPTED TO ENGAGE SAID GROOVE; FIRST MEANS INCLUDING A HOUSING FOR HOLDING SAID LATCH, A SPRING, AND GUIDE MEANS HAVING A CAVITY SPECIALLY SHAPED TO RECEIVE THE TIP OF SAID KEY, SAID FIRST MEANS BEING ADAPTED TO MAINTAIN SAID LATCH ARM IN ENGAGEMENT WITH SAID GROOVE AND TO ROTATE SAID LATCH ARM OUT OF ENGAGEMENT WITH SAID GROOVE AND INTO SAID HOUSING WHEN SAID KEY IS CAUSED TO MOVE SAID GUIDE MEANS WHICH THEREUPON COMPRESSES SAID SPRING AND MOVES SAID LATCH CAUSING SAID LATCH ARM SO TO ROTATE; AND SECOND MEANS THREADABLY FASTENED TO SAID HOUSING AND HAVING A SHOULDER TO ENGAGE SAID LIMIT STOP, A SPECIAL KEYWAY TO RECEIVE SAID KEY AND A CAVITY SPECIALLY SHAPED TO HOLD SAID KEY AXIALLY FIXED IN POSITION WHEN SAID KEY IS INSERTED THROUGH SAID KEYWAY, IS CAUSED TO MOVE SAID GUIDE MEANS AND IS ROTATED OUT OF ALIGNMENT WITH SAID KEYWAY, WHEREUPON SAID LATCH ASSEMBLY MAY BE WITHDRAWN FROM SAID CYLINDER BY PULLING SAID FIXED-IN-POSITION KEY OUTWARDS. 